1. Field of the Invention
The present invention relates to a method of manufacturing a vertical (vertical electrode type) GaN-based light emitting diode (LED). In the vertical GaN-based LED, a light emitting structure having a GaN layer and an active layer can be divided into LEDs without damage.
2. Description of the Related Art
Generally, GaN-based LEDs are formed by growing a light emitting structure on a sapphire substrate. However, because a sapphire substrate is rigid and electrically nonconductive and has a low thermal conductivity, it is difficult to reduce the size of the GaN-based LED for cost-down or improve the optical power and chip characteristics. Particularly, heat dissipation is very important for the LEDs because a large current should be applied to the GaN-based LEDs so as to increase the optical power of the GaN-based LEDs.
To solve these problems, a vertical GaN-based LED has been proposed. The vertical GaN-based LED is obtained by removing the sapphire substrate from the general GaN-based LED by a laser lift-off (hereinafter, referred to as LLO) technology.
The conventional vertical LED will be described in detail with reference to FIGS. 1A to 1F.
FIGS. 1A to 1F are sectional views illustrating a method of manufacturing a conventional vertical GaN-based LED.
Referring to FIG. 1A, a light emitting structure 160 including GaN-based semiconductor layers is formed on a transparent substrate 100 such as a sapphire substrate. The light emitting structure 160 includes an n-type GaN-based semiconductor layer 110, a GaN/InGaN active layer 120 having a multi-quantum well structure, and a p-type GaN-based semiconductor layer 130.
Referring to FIG. 1B, a photosensitive layer pattern 210 is formed on the p-type GaN-based semiconductor layer 130 to define LED regions having a desired size.
Referring to FIG. 1C, the light emitting structure 160 is divided into equal sections with the size of LEDs by dry etching (e.g., inductive coupled plasma (ICP) dry etching) using the photoconductive layer pattern 210 as an etch mask.
To divide the light emitting structure 160, the light emitting structure 160 is dry etched until the substrate 100 on which the light emitting structure 100 is formed is exposed. In this case, however, the n-type GaN-based semiconductor layer 110, the active layer 120, and the p-type GaN-based semiconductor layer 130 of the light emitting structure 160 can be cracked or damaged because they are exposed to the plasma for a long time. Thus, the characteristics of the LED can be deteriorated.
Referring to FIG. 1D, positive electrodes (p-electrodes) 140 are formed on the sections of the light emitting structure 160, respectively. Next, referring to FIG. 1E, a structure support layer 150 is formed on the p-electrodes 140.
Referring to FIG. 1F, the substrate 100 is removed by an LLO process. Then, negative electrodes (n-electrodes) (not shown) are formed on the exposed N-type GaN-based semiconductor layer 110. In this way, a vertical GaN-based LED is formed.
As described above, when the vertical GaN-based LED is formed by the related art method, the characteristics and reliability of the vertical GaN-based LED are deteriorated due to the above-described problems. Consequently, the process yield of the LED is reduced.